Downhole tools such as driving units, strokers, perforators etc. are exposed to extreme pressure differences between the inside and outside of the tools. In order to avoid collapses by implosion or explosion of the tools, which might damage both tools and well structure and furthermore lead to production stops in the wells, pressure compensating devices have been well-known for decades within this field. To accommodate pressure compensation, borehole fluid is typically allowed inside the tool on one side of the pressure compensating device and hydraulic fluids typically maintained inside a downhole tool will be on the other side, thereby equalising the two pressures on each side of the pressure compensating device.
A variety of pressure compensating devices are known using rubber bags, diaphragms, bellows and springs in the pressure compensating mechanism. However, they suffer from being designed to withstand a certain pressure difference, which when exceeded leads to a breakdown of the mechanism.
Increased reliability and a more fail-safe mechanism of a pressure compensating device for use in boreholes would therefore lead to optimised drilling and production performance, thereby minimising costs and maximising return of well operations. Since several types of tools require pressure compensation during borehole operations, various different processes would benefit from an improved pressure compensating device, all leading to a minimised risk of limitation in production time.
Thus, there is a need to be able to compensate pressures in downhole tools during exploration, production and monitoring of subsurface deposits, such as oil and gas deposits.